The WordPress Code Reference is an online resource for WordPress. It is auto generated and helps developers find more information on WordPress functions, classes, hooks, and more.
the_date(): By default, this function will output the date if the current post's date is different from the previous one output.
Parameters for the_date() are: $format, $before, $after, $echo.
In summary, the WordPress Code Reference is very reliable and has information on most, if not all the WordPress functions, classes, hooks, and methods. They have a section that shows what is new and updated on the latest WordPress version.